37 research outputs found
A triple-band antenna array for next-generation wireless and satellite-based applications
In this paper, a triple-band 1 × 2 and 1 × 4 microstrip patch antenna array for next-generation wireless and satellite-based applications are presented. The targeted frequency bands are 3.6, 5.2 and 6.7 GHz, respectively. Simple design procedures and optimization techniques are discussed to achieve better antenna performance. The antenna is designed and simulated using Agilent ADS Momentum using FR4 substrate (r = 4.2 and h = 1.66 mm). The main patch of the antenna is designed for 3.6 GHz operation. A hybrid feed technique is used for antenna arrays with quarter-wave transformer-based network to match the impedance from the feed-point to the antenna to 50. The antenna is optimized to resonate at triple-bands by using two symmetrical slits. The single-element triple-band antenna is fabricated and characterized, and a comparison between the simulated and measured antenna is presented. The achieved simulated impedance bandwidths/gains for the 1 × 2 array are 1.67%/7.75, 1.06%/7.7, and 1.65%/9.4 dBi and for 1 × 4 array are 1.67%/10.2, 1.45%/8.2, and 1.05%/10 dBi for 3.6, 5.2, and 6.7 GHz bands, respectively, which are very practical. These antenna arrays can also be used for advanced antenna beam-steering systems. Copyright © Cambridge University Press and the European Microwave Association 2014
Damped Bogoliubov excitations of a condensate interacting with a static thermal cloud
We calculate the damping of condensate collective excitations at finite
temperatures arising from the lack of equilibrium between the condensate and
thermal atoms. We neglect the non-condensate dynamics by fixing the thermal
cloud in static equilibrium. We derive a set of generalized Bogoliubov
equations for finite temperatures that contain an explicit damping term due to
collisional exchange of atoms between the two components. We have numerically
solved these Bogoliubov equations to obtain the temperature dependence of the
damping of the condensate modes in a harmonic trap. We compare these results
with our recent work based on the Thomas-Fermi approximation.Comment: 9 pages, 3 figures included. Submitted to PR
Thermodynamics of an interacting trapped Bose-Einstein gas in the classical field approximation
We present a convenient technique describing the condensate in dynamical
equilibrium with the thermal cloud, at temperatures close to the critical one.
We show that the whole isolated system may be viewed as a single classical
field undergoing nonlinear dynamics leading to a steady state. In our procedure
it is the observation process and the finite detection time that allow for
splitting the system into the condensate and the thermal cloud.Comment: 4 pages, 4 eps figures, final versio
A triple-band antenna array for next-generation wireless and satellite-based applications
In this paper, a triple-band 1 × 2 and 1 × 4 microstrip patch antenna array for next-generation wireless and satellite-based applications are presented. The targeted frequency bands are 3.6, 5.2 and 6.7 GHz, respectively. Simple design procedures and optimization techniques are discussed to achieve better antenna performance. The antenna is designed and simulated using Agilent ADS Momentum using FR4 substrate (r = 4.2 and h = 1.66 mm). The main patch of the antenna is designed for 3.6 GHz operation. A hybrid feed technique is used for antenna arrays with quarter-wave transformer-based network to match the impedance from the feed-point to the antenna to 50. The antenna is optimized to resonate at triple-bands by using two symmetrical slits. The single-element triple-band antenna is fabricated and characterized, and a comparison between the simulated and measured antenna is presented. The achieved simulated impedance bandwidths/gains for the 1 × 2 array are 1.67%/7.75, 1.06%/7.7, and 1.65%/9.4 dBi and for 1 × 4 array are 1.67%/10.2, 1.45%/8.2, and 1.05%/10 dBi for 3.6, 5.2, and 6.7 GHz bands, respectively, which are very practical. These antenna arrays can also be used for advanced antenna beam-steering systems. Copyright © Cambridge University Press and the European Microwave Association 2014
Mean field effects in a trapped classical gas
In this article, we investigate mean field effects for a bosonic gas
harmonically trapped above the transition temperature in the collisionless
regime. We point out that those effects can play also a role in low dimensional
system. Our treatment relies on the Boltzmann equation with the inclusion of
the mean field term.
The equilibrium state is first discussed. The dispersion relation for
collective oscillations (monopole, quadrupole, dipole modes) is then derived.
In particular, our treatment gives the frequency of the monopole mode in an
isotropic and harmonic trap in the presence of mean field in all dimensions.Comment: 4 pages, no figure submitted to Phys. Rev.
Finite temperature excitations of a trapped Bose-Fermi mixture
We present a detailed study of the low-lying collective excitations of a
spherically trapped Bose-Fermi mixture at finite temperature in the
collisionless regime. The excitation frequencies of the condensate are
calculated self-consistently using the static Hartree-Fock-Bogoliubov theory
within the Popov approximation. The frequency shifts and damping rates due to
the coupled dynamics of the condensate, noncondensate, and degenerate Fermi gas
are also taken into account by means of the random phase approximation and
linear response theory. In our treatment, the dipole excitation remains close
to the bare trapping frequency for all temperatures considered, and thus is
consistent with the generalized Kohn theorem. We discuss in some detail the
behavior of monopole and quadrupole excitations as a function of the Bose-Fermi
coupling. At nonzero temperatures we find that, as the mixture moves towards
spatial separation with increasing Bose-Fermi coupling, the damping rate of the
monopole (quadrupole) excitation increases (decreases). This provides us a
useful signature to identify the phase transition of spatial separation.Comment: 10 pages, 8 figures embedded; to be published in Phys. Rev.
Pairing in two-dimensional boson-fermion mixtures
The possibilities of pairing in two-dimensional boson-fermion mixtures are
carefully analyzed. It is shown that the boson-induced attraction between two
identical fermions dominates the p-wave pairing at low density. For a given
fermion density, the pairing gap becomes maximal at a certain optimal boson
concentration. The conditions for observing pairing in current experiments are
discussedComment: 10 pages, 5 figs, revtex
A selective ATP-binding cassette subfamily G member 2 efflux inhibitor revealed via high-throughput flow cytometry
Chemotherapeutics tumor resistance is a principal reason for treatment failure, and clinical and experimental data indicate that multidrug transporters such as ATP-binding cassette (ABC) B1 and ABCG2 play a leading role by preventing cytotoxic intracellular drug concentrations. Functional efflux inhibition of existing chemotherapeutics by these pumps continues to present a promising approach for treatment. A contributing factor to the failure of existing inhibitors in clinical applications is limited understanding of specific substrate/inhibitor/pump interactions. We have identified selective efflux inhibitors by profiling multiple ABC transporters against a library of small molecules to find molecular probes to further explore such interactions. In our primary screening protocol using JC-1 as a dual-pump fluorescent reporter substrate, we identified a piperazine-substituted pyrazolo[1,5-a]pyrimidine substructure with promise for selective efflux inhibition. As a result of a focused structure-activity relationship (SAR)-driven chemistry effort, we describe compound 1 (CID44640177), an efflux inhibitor with selectivity toward ABCG2 over ABCB1. Compound 1 is also shown to potentiate the activity of mitoxantrone in vitro as well as preliminarily in vivo in an ABCG2-overexpressing tumor model. At least two analogues significantly reduce tumor size in combination with the chemotherapeutic topotecan. To our knowledge, low nanomolar chemoreversal activity coupled with direct evidence of efflux inhibition for ABCG2 is unprecedented
Prevalence of Age-Related Macular Degeneration in Europe: The Past and the Future
Purpose Age-related macular degeneration (AMD) is a frequent, complex disorder in elderly of European ancestry. Risk profiles and treatment options have changed considerably over the years, which may have affected disease prevalence and outcome. We determined the prevalence of early and late AMD in Europe from 1990 to 2013 using the European Eye Epidemiology (E3) consortium, and made projections for the future. Design Meta-analysis of prevalence data. Participants A total of 42 080 individuals 40 years of age and older participating in 14 population-based cohorts from 10 countries in Europe. Methods AMD was diagnosed based on fundus photographs using the Rotterdam Classification. Prevalence of early and late AMD was calculated using random-effects meta-analysis stratified for age, birth cohort, gender, geographic region, and time period of the study. Best-corrected visual acuity (BCVA) was compared between late AMD subtypes; geographic atrophy (GA) and choroidal neovascularization (CNV). Main Outcome Measures Prevalence of early and late AMD, BCVA, and number of AMD cases. Results Prevalence of early AMD increased from 3.5% (95% confidence interval [CI] 2.1%–5.0%) in those aged 55–59 years to 17.6% (95%
The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set
Background
Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables.
Methods
Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set.
Results
Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001).
Conclusions
The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy